Bridge Design Guides for Recycled Structural Plastic Composite Prepared by Parsons Brinckerhoff, Inc.
1. Introduction
The design guide defines the practice to be followed in the design of thermoplastic members and provides useful commentary on the engineering mechanics of thermoplastic composite products. The Guidelines presented in this document summarizes the criteria and procedures used for thermoplastic bridges. Since Thermoplastic is a relatively new material for bridges, extra care is being taken in allowable design stresses as well as design details. Other structural grade plastic specifications have been consulted and adopted, as applicable. Specific projects will need their own guidelines
2. Definitions and Terminology (see also Appendix A)
AASHTO – AASHTO – American American Association of State Highway and Transportation Officials AREMA – AREMA – American American Railway Engineering and Maintenance-of-way Associations ASD – ASD – Allowable Allowable Stress Design: Both AREMA manual and AASHTO Standard Specifications deal with ASD method. Beam – Beam – aa main longitudinal structural member supported at each end, subject to bending and shear stresses incurred by various design loads including live loads. Bearing Pad – Pad – Elastomeric Elastomeric pad located on the substructure supporting the superstructure to promote even load distribution but also to accommodate vertical and rotational movements of beams. Bearing Stiffener – Stiffener – A A vertical member placed between top flange and bottom flange of girders to enhance stability, increase load-bearing capability and provide stiffness to the girder Bridge Railing – Railing – A A combination of posts and railings to keep vehicles on the bridge.
Cover Panels – Panels – Panels Panels located on top of I-beams to improve structural capacity of the beams. The panels are attached to top flange with glue and screws. Cross Ties – Ties – Railroad Railroad cross ties located on top of beams directly to support railroad rails. It should be strong enough to support the various design loads. Curb – Curb – aa rectangular member longitudinally placed on both ends of railroad cross ties. Deck Slab – Slab – The The riding surface for vehicles at the top of a bridge. Deck slab is supported by a group of beams. Many times an overlay is placed on top of the deck slab. J-Bolt – J-Bolt – A A fastener that provides mechanical connection between cross ties and beams. Overlay – Overlay – Material Material placed on top of the deck slab to protect the deck slab from the environment and provide a smooth riding surface. Piles – Piles – A A load bearing element penetrating into the ground to support a bridge structure Pile Cap – Cap – A A structural member connected to a group of piles enabling it to act as a single unit to support the imposed bridge loads. Longitudinal Shear Block – a – a blocking member located underneath beams to restrain longitudinal movement of beams in relation to the pier cap. Tie Rod – Rod – Stainless Stainless steel rod that connects a number of beams sitting side-by-side to promote monolithic performance behavior as they carry the bridge design loads. Transverse Connector – Connector – A A horizontal member that connects a group of piles together to promote load-sharing and integral movement among connected piles within a pier Transverse Shear Block – Block – aa blocking member located on top of pier cap ends to restrain transverse movement of bridge superstructure.
3. Standards and Specifications In the absence of specifications that can be directly applied to thermoplastic material, AREMA Manual for railroad bridges and the ASD method from AASHTO Standard Specifications for highway bridges shall be utilized in the design. AASHTO LRFD Specifications will not be utilized until resistance factors of thermoplastic material are developed.
4. Geometrics 1) Span Arrangement in Longitudinal Direction The bridge span length between two piers is determined by considering various stresses of structural members and deflection limit of the main beams. Details of allowable stresses and deflection limit are discussed in other sections of this design guide.
A simply supported span generates maximum positive moment at mid-span but produces zero uplift at the supports. The use of continuous spans reduces maximum positive moment at mid-span but produces negative moment at piers and uplift force at each beam end. Proper restraining mechanism should be implemented at each support where uplift movement is expected. 2) Beam Arrangement in Transverse Direction The arrangement of the main beams in transverse direction is made by considering how widely the live load is transferred to the beams. For preliminary design of railroad bridges, for example, use 1:1 load transferring dispersion from top of cross ties to the beams. Beams within the load dispersion are assumed to equally share the live load. For highway bridge design, consider a side-by-side arrangement since the wheel loads of highway traffic are not stationary in transverse direction. 3) Clearances Based on the bridge location both horizontal and vertical clearances shall be provided according to local requirements. 4) Alignment and Elevations Either the rail road or highway alignment shall be maintained on the bridge. The bridge shall meet the requirements of the rail profile or the highway profile, as applicable.
5. Material Properties 1) Thermoplastic Formulations The thermoplastic composite used for vehicular bridges and railroad bridges is made out of immiscible polymer blend of High-density polyethylene (HDPE) with polypropylene encapsulated glass fiber reinforcement. The detailed descriptions are provided in General Specifications for RSPC material.
2) Testing methods for Thermoplastic The following ASTM methods apply: Flexure: ASTM D6109 Tension: ASTM D638 Compression: ASTM D695 Shear: ASTM D6109 Thermal Expansion: ASTM D696 Modulus of Elasticity ASTM D6108
3) Ultimate Stresses and Allowable Stresses The applied stresses incurred in thermoplastic structural members shall not exceed the following allowable stresses:
Flexure: Tension : Compression: Shear:
Ultimate Stress 2,500 psi 3,000 psi 3,500 psi 1,100 psi
Allowable Stress 600 psi 600 psi 600 psi 350 psi
The allowable stresses can be increased for certain load combinations due to their frequency of occurrence. See Section for Load Load and Load combinations for detail. 4) Thermal Expansion Careful consideration should be taken for thermal movement in thermoplastic bridge design due to considerably large coefficient of thermal expansion compared to conventional construction materials.
Coefficient of Thermal Expansion:
0.0000282 in./in./deg F
5) Modulus of Elasticity Two moduli of elasticity are considered depending on conditions of application: Static Modulus of Elasticity: 250 ksi for general stresses Dynamic Modulus of Elasticity: 350 ksi for live load deflection
6) Glues
For I-Beams – I-Beams – 3M 3M Scotch-Weld Structural Plastic Adhesive DP-8010 series or Loctite 3034, or equivalent For Bearing Stiffeners and miscellaneous – Gorilla – Gorilla glue, a multipurpose polyurethane adhesive that has ANSI/HPVA Type I rating for waterproof.
7) Fasteners Materials for fasteners shall conform to ASTM grade A36. Bolts, nuts and washers: – Used at I-Beams, Curbs and Tie Rods – Bolts shall conform to the requirements of ASTM A307 except where high-strength or other special types of bolts are required. – Nuts for bolts conforming to the requirements of A307 shall conform to the requirements of ASTM A563. – Washers shall conform to the requirements of ASTM F844. Lock washers shall conform to the requirements of ANSI B18.21.1. – Galvanization of steel anchor bolts, nuts, and washers shall conform to the requirements of ASTM A153.
Screws: – Used at Cover Panels and Longitudinal Shear Blocks – Galvanized screws are not recommended. Stainless steel screws are recommended, with pre-drilling of the holes to avoid material residue buildup.
6. Design Method and Considerations
1) Design Method Allowable Stress Design (ASD) method is adopted for thermoplastic material. Load Factor Design (LFD) and Load & Resistance Factor Design (LRFD) methods are not presently appropriate for this type of material due to its viscoelastic behavior and lack of enough data for resistance factors. The total load effects produced by the unfactored loads shall not be greater than the allowable stresses in ASD method. 2) Loads and Load Combinations Thermoplastic structural elements shall be designed to safely support all anticipated loads. Minimum design loads and load combinations shall be determined in accordance with the applicable design specifications or design manual. For loads on highway bridges, AASHTO Standard Specifications should be used to calculate the minimum design loads and AREMA manual should be utilized for loads of railroad bridges. (See Appendix A, Figure 2.) For bridges, the loads to be considered include Dead load (D), Live load (L), Impact (I), Centrifugal Force (CF), Earth pressure (E), Buoyancy (B), Wind load on structure (W), Wind load on Live load (WL), Longitudinal Force (LF), Longitudinal force due to Friction (F), Earthquake (EQ), Stream Flow (SF), Ice pressure (ICE) and Other forces including Shortening, Shrinkage, Temperature Temperature and Settlement of Supports (OF). In general, Cooper E80 load or client-defined load is used for the design of railroad bridges and HS25 or HS20 load for highway bridges. In the ASD method, certain load combinations allow the designer to increase the loadbearing capacity of the material depending on the probability of occurrence. Table 1 presents load combinations and allowable increase of basic unit stress for railroad th structures. Table 3.22.1A of AASHTO Standard Specifications 17 Edition can be applied for highway structures.
Table 1: Group Loading Combinations – ASD – ASD method of AREMA
3) Thermal Expansion and Contraction Each thermoplastic structural member shall be designed not to cause structural or serviceability concerns due to thermal expansion or contraction and to meet the strength and stiffness criteria including any temperature effects. The range of temperature shall generally be as
Climate Moderate Cold
Temperature Rise 30 degree F 35 degree F
Temperature Fall 40 degree F 45 degree F
4) Piles
Preliminary number of piles per pier is determined by data from soil report. In order to calculate the pile loads, perform a frame analysis by modeling the entire pier along with pier cap and piles. Piles can be battered in longitudinal and transverse directions to provide more resistance. Final number of piles should be designed with consideration of both load capacity and serviceability serviceabilit y limit. Excessive pile deformation will impose additional stresses to pile supporting members.
5) Bearing Pad Elastomeric bearing pads are used to promote even load distribution and to accommodate vertical and rotational movements of beams at supports. – Follow AASHTO Standard Specifications for design and Specifications – Follow material selection for highway bridges. For railroad bridges, use design guide provided in the AREMA manual. Plain or laminated elastomeric bearing pad with 50 to 60 durometer hardness neoprene can be used for thermoplastic bridges.
6) Fasteners and Mechanical Connections Structural members shall be checked for various stresses at connections using commonly accepted analysis methods. When determining the stress for a given structural member, the net section shall be considered. The net area is calculated as the gross area minus the product of the actual width of fastener holes in the member and the thickness of the member as measured normal to the axis of the member.
All fasteners including steel bolts, drift bolts, lag screws, wood screws, nails and spikes shall be checked for flexure and/or shear limit using the latest specification for the fastener material.
7) Curbing & Guardrail Guardrails and curbs shall be designed to comply with AASHTO Standard Specifications and/or other local guidelines for impact loading. The construction of all curbing and rail is to be in compliance with the AASHTO and/or local requirements and guidelines.
8) Deflection Limitations Flexural members of bridge structures shall be designed to limit live load deflection within allowable ranges to prevent strength failure or serviceability failures of the structure. Since thermoplastic material is extremely strong in fatigue compared to other conventional construction materials, a designer can focus on other strength or serviceability failures such as spike-pull out due to severe rail movement. For railroad bridges the deflection limit is 1/600 of the span. For highway bridges the deflection is controlled by providing a minimum superstructure depth stipulated in Table 8.9.2 of AASHTO Standard th Specifications 17 Edition. When making deflection computation instead of using the table, the deflection due to service load plus impact shall not exceed 1/800 of the span. If the bridge is located in urban area and used in part by pedestrians, the ratio preferably shall not exceed 1/1000. More detailed methods of controlling live load deflection are discussed in AASHTO Standard Specifications for highway bridges and AREMA Manual for railroad bridges.
9) Construction Considerations Piles shall be installed with fixed leads. After pile cutoff, shims may be used to have a level pile cap installation.
7. Analysis Tools
Maximum stresses applied to each structural member should be calculated considering all possible loads and load combinations. Generally accepted structural analysis software such as STAAD or LARSA can be utilized to perform moving load analysis to find the maximum stresses applied to structural components. For simply supported span, tabulated values for live load reactions provided in AASHTO specifications and AREMA manuals can be conveniently utilized without going through the moving load analysis.
8. QA/QC process
It is imperative that Quality Assurance (Q/A), Quality Control (Q/C) and Constructability be followed to meet and/or exceed client expectations in delivery of the projects. The focus of quality reviews is to prevent, as much as possible, errors and omissions before projects are delivered to the client. The quality reviews are applicable to all studies, reports, drawings, specifications, design computations and cost estimates, and in general to all services provided by the design team. Quality Control is the detailed checking of the project deliverables to ensure that the deliverables comply with quality requirements of the client. All structural design packages will include: calculations, list of assumptions, specifications, references, methodology, computer input and results, conclusions, detailed sketches to aid in preparation of structural plans and summary. All structural design calculations furnished by the structural engineer will be checked by a competent structural engineer. Quality assurance is the review of the deliverables specified in the Q/C to ensure that deliverables at each stage are correct, appropriate and consistent; address all concerns; avoid ambiguities in specifications and meet the client’s requirements. QA is intended to do an overall review of the deliverables for consistency, overlooked details, completeness of the documents, sanity check of the details for their correctness and appropriateness to catch issues which may have been missed by the originator and checker. QA check of the project deliverables shall be done by a qualified senior professional engineer well experienced in the bridge and structures field. Constructability review is a process that is generally applied from the early design stages to the final design stages of the projects to ensure that the projects are constructible, well thought out for staging, provides flexibility to the contractor, addresses contractors concerns for access and lay-down areas while also being cost effective, biddable, and maintainable. This is a must for all complicated structures however this issue should be considered in all projects. Constructability reviews shall be performed by experienced personnel with expertise in the type of structure being designed.
Frequency of QC, QA and constructability checks should be established in the beginning of the project. Post Construction review is also vital to successfully complete a project. Client holds a meeting with the prime contractor after the project is finished. This provides an opportunity to discuss the success and difficulties of the project and what steps could be taken to mitigate the issues on future projects. A representative from the design team should attend this meeting and implement applicable suggestions on future projects. Purpose of the attendance in this meeting is to learn for indul ge in discussion of anyone’s responsibility on any future improvements improvement s if any and not to indulge issues. For detailed quality process practiced by PB, please refer to Appendix B.
Appendix A:
An Example of Thermoplastic Railroad Bridge and Railroad Live Loads
(a) Elevation (a) Elevation View
(a) Typical Section
Figure 1: Example of a Railroad Bridge
(a) Cooper E80 Axle Load Diagram
(b) Alternate (b) Alternate Live Load on 4 Axles
Figure 2: Cooper E80 and Alternate Live Load
Appendix B: Quality Manual For PB Bridges and Structures Personnel
Quality Manual for PB Bridges and Structures Personnel
1 PURPOSE PB is committed to provide its clients a quality product. Compliance with this guidance is to maintain a high level of quality and consistency of project deliverables among all bridge and structures Personnel in the U.S. Certain projects or Joint Ventures (JVs) may deviate from this procedure with the approval of the Director of Bridges. Sub-consultants are responsible for the quality of their deliverables and are expected to have a similar procedure in place. It is imperative that Quality in the forms of Quality Assurance (Q/A), Quality Control (Q/C) and Constructability be followed to meet and or exceed client expectations in delivery of the projects. The focus of quality reviews is to prevent, as much as possible, errors and omissions before projects are delivered to the client.
2 SCOPE This quality procedure is applicable to all studies, reports, drawings, specifications, design computations and cost estimates, and in general to all services provided by PB in the areas of bridges and structures in the U.S.
3 GENERAL The Director of Bridges for Americas Complex Bridge TEC or his/her designee is responsible to develop and maintain quality procedures, provide guidance and share the lessons learned from various projects.
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DEFINITIONS
Documents Project deliverables include studies, reports, drawings, specifications, calculations and cost estimates. Quality Control (Q/C) Quality Control is the detailed checking of the project deliverables such as plans, specifications, reports, studies and others. It is intended to ensure that the project deliverables comply with quality requirements of the client as well as that of PB/Project. Quality Assurance (Q/A) Quality assurance is the review of the deliverables specified in the Q/C to ensure that deliverables at each stage are correct, appropriate, consistent, address all concerns, avoid ambiguities in specifications and meet the PB/Project and client’s requirements.
Check-print A copy of a study, report, drawing or specification document in its pre-submission form used for the purpose of checking and recording additions, deletions, deletions, and corrections to the original document. document. The check-print is stamped as a check-print. Check-prints of submittal documents documents are retained in the contract file. Note: No updates to originals should should be made during during checking process, as much as possible. Constructability Reviews It is a process that is generally applied from the early design stages to the final design stages of the projects to ensure that the projects are constructible, well thought out for staging, provides flexibility to the contractor, addresses contractors concerns for access and lay-down areas while also being cost effective, biddable, and maintainable. This is a must for all complicated structures however this issue should be considered in all projects. Post Construction Reviews Client holds a meeting with the prime contractor after the project is finished. This provides an opportunity to discuss the success and difficulties of the pr oject and what steps could be taken to mitigate the issues on future projects. A representative from PB Structural staff should attend this meeting and implement implement applicable suggestions on future projects. Purpose of our attendance in this meeting is to learn for future improvements if any and not to indulge in discussion of anyone’s responsibility on any issues.
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ROLES AND RESPONSIBILITIES RESPONSIBILI TIES
The checking of studies, reports, drawings, specifications, calculations and cost estimates requires a minimum of two individuals: an originator/back-checker/corrector and a checker/verifier.
5.1 Project Manager (PM) – The PM is responsible for ensuring that this Quality procedure is implemented for all studies, reports, reports, drawings, specifications, calculations, calculations, and cost estimates related to their project, for establishing a schedule that allows checking to take place prior to internal or external distribution of the document, for assembling the check-prints, stamping and dating them and following them through the checking process, and for retaining original checked calculations after the documents have been checked and corrected.
5.2 Technical leads – The technical leads are responsible for maintaining check-prints available for future reference, update or audit.
5.3 Originator – The originator has the primary responsibility for accuracy and adequacy of the document. It is not intended that the originator rely on the checking process to complete complete the document. c hecker is independent of the originator and is responsible for checking the document. document . 5.4 Checker - The checker ( usually the originator) is responsible for reviewing the checked 5.5 Back-checker - The back-checker (usually document and confirming that the items marked as errors are indeed errors and that the corrections noted are indeed correct.
5.6 Corrector - The corrector (usually the originator) is responsible for ensuring that the changes marked on the check-print are made on the original document. ( usually the checker) is responsible for reviewing a copy of the corrected 5.7 Verifier - The verifier (usually document against the check-print and verifying that the corrections marked have been properly incorporated. incorporated.
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PROCESS
The Quality procedures will be followed by each member of Bridge and structural staff in the U.S. A written Quality plan must be developed for every project. Each state DOT/agency may have different quality plan/standards requirements. The more stringent plan of either PB or the client’s plan shall be followed. A check list must be developed that ensures all the items have been covered. A sample check-list is contained in the attachment. It is recommended that the check-list be adapted as necessary to cover the items pertaining to particular project.
Frequency of QC, QA and constructability checks should be established in the beginning of the project. It is recommended that documents be reviewed at a minimum before every established project milestone. milestone. QC reviews must be carried out by competent engineers who posses more experience than the originator. QA reviews shall be performed by senior level PB Engineers with expertise in the type of the structure considered. Constructability reviews shall be performed by experienced personnel with expertise in the type of structure being designed. For complex structural projects, independent peer review by engineers with the expertise in the type of structure from other offices should be considered.
6.1 Preparing the document for checking 6.1.1 Studies, Reports, Drawings, Specifications, Calculations and Cost Estimates As each document is completed in its final f orm and deemed ready for checking, the originator prepares a stamped check-print copy. copy. The check-print stamp is applied on the cover (or back of the cover, if space is an issue) of the study, report or specification section, on the front or back of each drawing, on the front cover of each set of calculations and cost estimates.
6.2 Checking 6.2.1 Studies, Reports, Drawings, Specifications, Calculations and Cost Estimates The following color-coding applies to the checking of all documents. The checker (a qualified individual independent of the originator) reviews each check -print for technical adequacy and conformance to applicable standards and format, including performing specific accuracy checks for that type of document. The checking activity is recorded directly on the the check-print through the use of YELLOW pencil or highlighter for those features found to be correct and RED pencil for features found to be in error. For features found to be in error, the correct information is recorded, recorded, in red pencil, in a manner that makes it clear to the corrector what needs to be changed. Red, yellow, green or blue are not used to note comments, questions or other instructions. instructions. These colors are reserved for the checking process. Comments or instructions instructions are written in black, using either a cloud or leader line to indicate a checking comment. Such comments are resolved, if necessary, in discussions between the checker and originator and resolutions are indicated on the check-print. Upon completion of of the check of each check-print, the checker signs signs and dates the check-print check-print stamp. In the case of calculations, the checker signs and dates the “Checked By” area on the calculation sheet or cover sheet. In lieu of using color coding for checking of any deliverable documents a comment review form may be used. The form shall identify the checker, specific comments comments and include a space for disposition of the comment. The form shall be signed by the originator and checker after all comments have been resolved and incorporated. A copy of the form shall be kept with the final document in the project files. 6.3 Back-checking 6.3.1 Studies, Reports, Drawings and Specifications The following color-coding applies to the back-checking of all documents. The back-checker (usually the originator) reviews the checker’s marked changes on the check -print. To record the process, the back-checker:
Checks in GREEN pencil each of the checker’s changes, if in agreement that the orig inal should be changed, and adds in GREEN, with the concurrence of the checker, any additional changes not picked up by the checker. Crosses out in GREEN each of the checker’s changes that the back -checker and checker agree need not be changed, leaving the checker’s marks intact. Signs and dates the check-print stamp.
The back-checker and checker resolve differences encountered during the checking process so they are clear for the corrector and not repeated in subsequent documents documents generated. If the two cannot achieve resolution, the appropriate discipline lead is asked to resolve the issue. 6.3.2 Calculations and Cost C ost Estimates For manual calculations, calculations are signed by the originator at the time of preparation and dated and then given to the checker. After the checker completes completes the checking, the originator/back-checker originator/back-checker reviews the comments, discusses any differences of opinion issues or seeks clarification, changes the calculations which are then reviewed by the checker checker for adequacy of change. Then the checker signs off the the
calculations and dates them. If significant or multiple changes are noted on a manual document, it may be completely replaced. If corrections are noted on an electronic document, the agreed-upon changes are incorporated and the revised document is printed-out and signed by the checker and originator/back-checker. Checker’s name should never be included in an electronic e lectronic document, as subsequent changes would appear as though they are already checked. The checker should always manually initial or sign the printed document. This step concludes the checking process associated with calculations and cost estimates. 6.4 Correcting Original Documents 6.4.1 Studies, Reports, Drawings and Specifications Correction of the original document is supervised or performed by either the back-checker or checker, since both know what needs to be changed. When making the changes to the original document, the corrector circles each correction on the checkprint in BLUE pencil as it is incorporated. The corrector signs and dates the check-print stamp upon completion of the corrections for each document. 6.4.2 Calculations and Cost C ost Estimates Calculations and cost estimates are subject to correction as indicated above. 6.5 Verifying Corrections to Studies, Reports, Drawings and Specifications The following color-coding applies to the verification of all documents. When corrections are completed, the verifier (either the originator/back-checker originator/back-checker or the checker) confirms that the corrections have been incorporated without error. If the corrections are not made or are incorrect, the clean print is marked in red with instructions and returned to the corrector. If the corrections have been made properly, the verifier circles each comment in blue on the check-print in green pencil and signs and dates the check-print stamp.
6.6 Disposition of Checked Documents The completed original documents for studies, reports, drawings, cost estimates and specifications are maintained in the Project Project Files. Their check-prints are kept by the Project Manager or Technical Leads Leads as determined by the PM. Calculations are placed in calculation books and maintained by the Project Manager or Technical Leads. 6.7 Subsequent Revisions If a document is subsequently revised after verification is complete, a new original is prepared and the checking process is reinitiated. The earlier check-print or hard copy original is marked VOID, although it may be used as a reference during the preparation of the revised document. The revised document is then stamped, checked and back-checked, back-checked, and the original corrected and verified verified as indicated above. If necessary, the revised document is reissued to the recipients of the original version with directions to discard the void version.
A Revision/Review History on the plan and or document as shown below must be maintained for future reference. Revision/Review History:
Rev
Rev 0
7
June 08
Date
Description
Checker Originator
Quality Assurance
Constructability Review
Preliminary Plans
STRUCTURAL DESIGN CALCULATIONS
The Originator, a structural engineer, will be responsible for preparation of all design calculations, generating computer aided results. All structural design packages will include: calculations, list of assumptions, specifications, references, methodology, computer input and results, conclusions, detailed sketches to aid in preparation of structural plans and summary. All structural design calculations furnished by the structural engineer will be developed in accordance with the following: 1. 2. 3. 4. 5. 6. 7.
8. 9. 10.
Design criteria established for the project. Current AASHTO specifications along with any other design requirements established by the client. The structure design must be checked for construction loads when applicable as loads during erection and staged construction may often govern the design. Any variation from AASHTO design specifications must be approved by the client and proper documentation in support of variations must be in the files. The design of foundations must be based on geotechnical report and any deviation must be justified and documented. Structural analysis shall take into consideration structural boundary conditions and discontinuities. The input data used in the computer analysis and some of the key design information such as load distribution factors, allowable bearing for foundation shall be independently checked by the originator and the checker. The independent checked set of calculations will then be used for input data for subsequent computer analysis. All design calculations shall be checked by a competent structural engineer. The original set of signed off checked calculations will be furnished to the project manager who will archive in the project files.
7.1 Structural Design Calculations w/ independent Checker 1. All the design computations and items identified in section 7 will be carried out by two structural engineers (designer and checker).An independent check is necessary for a complex bridge design and/or when required by the client. Any differences will be reconciled. The original set of calculations is then signed off by the checker. Both sets of calculations will become record sets and will be submitted to the client. 2. The checker and reviewer of the calculations and document must have experience and technical knowledge equivalent to or greater than the originator of the material. 3. At any stage of the design process a close tab should be kept to the original cost estimate of the project as listed in the preliminary design computations. Any variation in the cost estimate should be brought to the client’s attention.
7.2 Checking of Structural drawings 1. A sample example may be obtained from the client and drawings can be produced following the example. In general there should be enough details and information to build the structure. 2. All drawings must be thoroughly checked at each stage of drawing development. 3. It is recommended that the color coding system as recommended in DSL Policy No.2 be followed. 4. All the notes shown on the structural plan sheets should be checked thoroughly for consistency with other drawings within the set and also with project specifications and project special provisions to avoid conflicts.
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QUALITY ASSURANCE (QA) 1. QA check of the project deliverables shall be done by a qualified senior professional engineer well experienced in the bridge and structures field. 2. QA is not a substitute for Quality Control and Constructability reviews. QA is intended to do an overall review of the deliverables for consistency, overlooked details, completeness of the documents, sanity check of the details for their correctness and appropriateness to catch issues which may have been missed by the originator and checker since they are too close to the production of the documents. 3. QA checker shall use the red color for marking comments, green color for check of the corrected comments similar to the Quality Control process detailed above except for the Yellow color which indicated a item by item check of the contents of the deliverables. QA person is not expected to do detailed checking of the deliverables. 4. QA documents shall be also stored along with QC and constructability documents either with the PM or technical leads.
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CONSTRUCTABILITY ISSUES 1. 2.
Footings should be checked for any conflicts with underground utilities and or any other obstacles. Pile batters should be checked for any potential conflicts.
3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
Availability of the material need to be investigated. For instance 10 inches steel piles may be more readily available than 12 /14 inches steel piles or vice versa. Consider the delivery of the material for the structure. For example the existing site condition may not permit the delivery of the specified length of girder. Staged construction when applicable must match with corresponding roadway plans. Need to check if the structure can be built within available right of way Can the proposed bridge be constructed using normal construction techniques? Is enough staging area identified? Construction issues associated with project being constructed in phases. Any navigational issues Sequence of construction issues Fabrication/precasting and erection issues Other issues particular to the type of stru cture being designed
10 GENERAL ITEMS The items and issues will vary for each project. Following is a list of items as a guide to structural engineers in the development of check list. Items should be added or deleted as it fits the project.
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
Design exceptions. Construction staging. Traffic maintenance during construction. Soils information and footing recommendations. Right-of-Way limits and its impact on bridge construction. Any permit requirement (Coast Guard, Environmental, Environmental, Railroad, Utilities etc.) FHWA approval requirements. r equirements. Scour information. Old plans and / or sketch of the proposed work. Utilities- underground and overhead. Co-ordination with roadway plans. Railroads agreements and coordination. Documentation of any project changes as requested by the client. Vertical Clearance check. Horizontal clearance check
